Magnetic field sensor

ABSTRACT

Methods and apparatus for a magnetic field sensor for measuring movement of a target including a substrate and a magnet. A first bridge structure has first and second pluralities of magnetic field sensing elements spaced from each other. An axis of sensitivity of the magnetic field sensing elements is rotated at a predetermined angle with respect to an axis of rotation of the target to generate an output signal corresponding to the position of the target and a change in a property of the magnetic field generated by the magnet.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication No. 62/714,951, filed on Aug. 6, 2018, which is incorporatedherein by reference.

BACKGROUND

Various types of magnetic field sensing elements are known, includingHall Effect elements and magnetoresistance (MR) elements. Magnetic fieldsensors generally include a magnetic field sensing element and otherelectronic components. Some magnetic field sensors also include apermanent magnet (a hard ferromagnetic object) in a so-called “backbiased” arrangement.

Magnetic field sensors provide an electrical signal representative of asensed magnetic field. In some embodiments that have a back-bias magnet,the sensed magnetic field is a magnetic field generated by the magnet,in which case, in the presence of a moving ferromagnetic object, themagnetic field generated by the magnet and sensed by the magnetic fieldsensor varies in accordance with a shape or profile of the movingferromagnetic object. In contrast, magnetic field sensors that sense amoving magnet directly sense variations of magnetic field magnitude anddirection that result from movement of the magnet.

SUMMARY

Embodiments provide a back-biased magnetic field sensor with immunity tocommon mode fields. The sensor can include magnetoresistive sensingelements, which can be arranged in a bridge configuration, for sensing aferromagnetic target at first and second orientations. In a first mode,the magnetic sensor is positioned in a first orientation so that asensitive direction of the sensing elements is along a direction of atarget, such as a gear tooth. In a second mode, the magnetic sensor ispositioned in a second orientation to sense the variation of thedivergence of the magnetic flux lines coming from the back biasingmagnet.

In one aspect, a magnetic field sensor for measuring movement of atarget, the magnetic field sensor comprising: a substrate having a firstand second surfaces; a magnet disposed proximate to the first surface,wherein the magnet includes at least two poles to generate a magneticfield; and a first bridge structure having a first plurality of magneticfield sensing elements configured to generate a first magnetic fieldsignal indicative of a position of the target and a second plurality ofmagnetic field sensing elements configured to generate a second magneticfield signal indicative of the position of the target, wherein a firstpair of magnetic field sensing elements of the first plurality ofmagnetic field sensing elements are spaced a first distance from eachother and a second pair of magnetic field sensing elements of the secondplurality of magnetic field sensing elements are spaced a second,distance from each other, wherein an axis of sensitivity of the firstand second pluralities of magnetic field sensing elements is rotated ata predetermined angle with respect to an axis of rotation of the target,and wherein the first bridge structure is configured to generate anoutput signal based on the first magnetic field signal and the secondmagnetic field signal, the output signal corresponding to the positionof the target and a change in a property of the magnetic field generatedby the magnet.

A magnetic field sensor can include one or more of the followingfeatures: first and second magnetic field sensing elements of the firstplurality of magnetic field sensing elements are spaced equidistant froma first center axis of the magnet, first and second magnetic fieldsensing elements of the second plurality of magnetic field sensingelements are spaced equidistant from a first center axis of the magnet,the first distance between first pair of magnetic field sensing elementsof the first plurality of magnetic field sensing elements is less thanthe second distance between second pair of magnetic field sensingelements of the second plurality of magnetic field sensing elements,first and second magnetic field sensing elements of the first pluralityof magnetic field sensing elements are spaced equidistant from a firstcenter axis of the magnet and third and fourth magnetic field sensingelements of the first plurality of magnetic field sensing elements arespaced equidistant from the first center axis of the magnet, and whereinthe first and third magnetic field sensing elements are spacedequidistant from a second center axis of the magnet and the second andfourth magnetic field sensing elements are spaced equidistant from thesecond center axis of the magnet, first and second magnetic fieldsensing elements of the second plurality of magnetic field sensingelements are spaced equidistant from a first center axis of the magnetand third and fourth magnetic field sensing elements of the secondplurality of magnetic field sensing elements are spaced equidistant fromthe first center axis of the magnet, and wherein the first and thirdmagnetic field sensing elements are spaced equidistant from a secondcenter axis of the magnet and the second and fourth magnetic fieldsensing elements are spaced equidistant from the second center axis ofthe magnet, a second bridge structure having a third plurality ofmagnetic field sensing elements and a fourth plurality of magnetic fieldsensing elements, wherein a first pair of magnetic field sensingelements of the third plurality of magnetic field sensing elements arespaced a first distance from each other and a second pair of magneticfield sensing elements of the fourth plurality of magnetic field sensingelements are spaced a second, different distance from each other, thefirst magnetic field signal corresponds to a first degree of contractionof the magnetic field generated by the magnet in response to theposition of the target and the second magnetic field signal correspondsto a second, different degree of contraction of the magnet fieldgenerated by the magnet in response to the position of the target, acircuit coupled to the first bridge structure, wherein the circuitcomprises a comparison device having a first input coupled to a firstoutput of the first bridge structure to receive the first magnetic fieldsignal and a second input coupled to a second output of the first bridgestructure to receive the second magnetic field signal, the circuitfurther comprises an offset module coupled to the first and secondoutputs of the first bridge structure, wherein the offset module isconfigured to provide an offset adjustment to the first and secondmagnetic field signals, the circuit further comprises a converter modulehaving an input coupled to the output of the comparison device, the axisof sensitivity of the first and second plurality of magnetic fieldsensing elements is perpendicular to the axis of rotation of the target,the predetermined angle ranges from about 0 degrees with respect to theaxis of rotation of the target to about 90 degrees with respect to theaxis of rotation of the target, the first plurality of magnetic fieldsensing elements comprises a first plurality of magnetoresistanceelements and the second plurality of magnetic field sensing elementscomprises a second plurality of magnetoresistance elements, and/or thefirst and second pluralities of magnetoresistance elements comprise oneor more of giant magnetoresistance (GMR) elements, anisotropicmagnetoresistance (AMR) elements, tunneling magnetoresistance (TMR)elements or magnetic tunnel junction (MTJ) elements.

In another aspect, a method for measuring movement of a target, themethod comprises: positioning a magnetic field sensor relative to thetarget, wherein the magnetic field sensor includes: a substrate having afirst and second surfaces; a magnet disposed proximate to the firstsurface, wherein the magnet includes at least two poles to generate amagnetic field; and a first bridge structure having first and secondpluralities of magnetic field sensing elements, wherein a first pair ofmagnetic field sensing elements of the first plurality of magnetic fieldsensing elements are spaced a first distance from each other and asecond pair of magnetic field sensing elements of the second pluralityof magnetic field sensing elements are spaced a second, distance fromeach other, and wherein an axis of sensitivity of first and secondpluralities of magnetic field sensing elements is rotated at apredetermined angle with respect to an axis of rotation of the target;and generating a first magnetic field signal indicative by the firstplurality of magnetic field sensing elements, wherein the first magneticfield structure is indicative of a position of the target; generating asecond magnetic field signal by the second plurality of magnetic fieldsensing elements, wherein the second magnetic field signal indicative ofthe position of the target; generating an output signal based on thefirst magnetic field signal and the second magnetic field signal,wherein the output signal corresponds to the position of the target anda change in a property of the magnetic field generated by the magnet.

A method can further include one or more of the following features:spacing first and second magnetic field sensing elements of the firstplurality of magnetic field sensing elements equidistant from a firstcenter axis of the magnet, spacing first and second magnetic fieldsensing elements of the second plurality of magnetic field sensingelements equidistant from a first center axis of the magnet, the firstdistance between the first pair of magnetic field sensing elements ofthe first plurality of magnetic field sensing elements is less than thesecond distance between the second pair of magnetic field sensingelements of the second plurality of magnetic field sensing elements,first and second magnetic field sensing elements of the first pluralityof magnetic field sensing elements are spaced equidistant from a firstcenter axis of the magnet and third and fourth magnetic field sensingelements of the first plurality of magnetic field sensing elements arespaced equidistant from the first center axis of the magnet, and whereinthe first and third magnetic field sensing elements are spacedequidistant from a second center axis of the magnet and the second andfourth magnetic field sensing elements are spaced equidistant from thesecond center axis of the magnet, first and second magnetic fieldsensing elements of the second plurality of magnetic field sensingelements are spaced equidistant from a first center axis of the magnetand third and fourth magnetic field sensing elements of the secondplurality of magnetic field sensing elements are spaced equidistant fromthe first center axis of the magnet, and wherein the first and thirdmagnetic field sensing elements are spaced equidistant from a secondcenter axis of the magnet and the second and fourth magnetic fieldsensing elements are spaced equidistant from the second center axis ofthe magnet, the magnetic field sensor comprises a second bridgestructure having a third plurality of magnetic field sensing elementsand a fourth plurality of magnetic field sensing elements, wherein afirst pair of magnetic field sensing elements of the third plurality ofmagnetic field sensing elements are spaced a first distance from eachother and a second pair of magnetic field sensing elements of the fourthplurality of magnetic field sensing elements are spaced a second,different distance from each other, the first magnetic field signalcorresponds to a first degree of contraction of the magnetic fieldgenerated by the magnet in response to the position of the target andthe second magnetic field signal corresponds to a second, differentdegree of contraction of the magnet field generated by the magnet inresponse to the position of the target, the magnetic field sensorfurther comprises a circuit coupled to the first bridge structure,wherein the circuit comprises a comparison device having a first inputcoupled to a first output of the first bridge structure to receive thefirst magnetic field signal and a second input coupled to a secondoutput of the first bridge structure to receive the second magneticfield signal, providing an offset adjustment, by an offset module, thefirst and second magnetic field signals, converting a comparison signalgenerated by the comparison device from an analog signal to a digitalsignal, the axis of sensitivity of the first and second plurality ofmagnetic field sensing elements is perpendicular to the axis of rotationof the target, the predetermined angle ranges from about 0 degrees withrespect to the axis of rotation of the target to about 90 degrees withrespect to the axis of rotation of the target, the first plurality ofmagnetic field sensing elements comprises a first plurality ofmagnetoresistance elements and the second plurality of magnetic fieldsensing elements comprises a second plurality of magnetoresistanceelements, and/or the first and second pluralities of magnetoresistanceelements comprise one or more of giant magnetoresistance (GMR) elements,anisotropic magnetoresistance (AMR) elements, tunnelingmagnetoresistance (TMR) elements or magnetic tunnel junction (MTJ)elements.

In another aspect, a magnetic field sensor for measuring movement of atarget, the magnetic field sensor comprises: a substrate having a firstand second surfaces; a means for generating a magnetic field disposedproximate to the first surface, wherein the means for generatingincludes at least two poles; and a first sensing means having a firstplurality of magnetic field sensing means configured to generate a firstmagnetic field signal indicative of a position of the target and asecond plurality of magnetic field sensing means configured to generatea second magnetic field signal indicative of the position of the target,wherein a first pair of magnetic field sensing means of the firstplurality of magnetic field sensing means are spaced a first distancefrom each other and a second pair of magnetic field sensing means of thesecond plurality of magnetic field sensing means are spaced a second,different distance from each other; wherein an axis of sensitivity ofthe first and second pluralities of magnetic field sensing means isrotated at a predetermined angle with respect to an axis of rotation ofthe target, and wherein the first sensing means is configured togenerate an output signal based on the first magnetic field signal andthe second magnetic field signal, the output signal corresponding to theposition of the target and a change in a property of the magnetic fieldgenerated by the means for generating.

A magnetic field sensor can further include one or more of the followingfeatures: first and second magnetic field sensing means of the firstplurality of magnetic field sensing means are spaced equidistant from afirst center axis of the means for generating, first and second magneticfield sensing means of the second plurality of magnetic field sensingmeans are spaced equidistant from a first center axis of the means forgenerating, the first distance between first pair of magnetic fieldsensing means of the first plurality of magnetic field sensing means isless than the second distance between second pair of magnetic fieldsensing means of the second plurality of magnetic field sensing means,first and second magnetic field sensing means of the first plurality ofmagnetic field sensing means are spaced equidistant from a first centeraxis of the means for generating and third and fourth magnetic fieldsensing means of the first plurality of magnetic field sensing means arespaced equidistant from the first center axis of the means forgenerating, and wherein the first and third magnetic field sensing meansare spaced equidistant from a second center axis of the means forgenerating and the second and fourth magnetic field sensing means arespaced equidistant from the second center axis of the means forgenerating, first and second magnetic field sensing means of the secondplurality of magnetic field sensing means are spaced equidistant from afirst center axis of the means for generating and third and fourthmagnetic field sensing means of the second plurality of magnetic fieldsensing means are spaced equidistant from the first center axis of themeans for generating, and wherein the first and third magnetic fieldsensing means are spaced equidistant from a second center axis of themeans for generating and the second and fourth magnetic field sensingmeans are spaced equidistant from the second center axis of the meansfor generating, a second sensing means having a third plurality ofmagnetic field sensing means and a fourth plurality of magnetic fieldsensing means, wherein a first pair of magnetic field sensing means ofthe third plurality of magnetic field sensing means are spaced a firstdistance from each other and a second pair of magnetic field sensingmeans of the fourth plurality of magnetic field sensing means are spaceda second, different distance from each other, the first magnetic fieldsignal corresponds to a first degree of contraction of the magneticfield generated by the means for generating in response to the positionof the target and the second magnetic field signal corresponds to asecond, different degree of contraction of the magnet field generated bythe means for generating in response to the position of the target, acircuit coupled to the first bridge structure, wherein the circuitcomprises a comparison device having a first input coupled to a firstoutput of the first sensing means to receive the first magnetic fieldsignal and a second input coupled to a second output of the firstsensing means to receive the second magnetic field signal, the circuitfurther comprises an offset module coupled to the first and secondoutputs of the first sensing means, wherein the offset module isconfigured to provide an offset adjustment to the first and secondmagnetic field signals, the circuit further comprises a converter modulehaving an input coupled to the output of the comparison device, the axisof sensitivity of the first and second plurality of magnetic fieldsensing means is perpendicular to the axis of rotation of the target,the predetermined angle ranges from about 0 degrees with respect to theaxis of rotation of the target to about 90 degrees with respect to theaxis of rotation of the target, the first plurality of magnetic fieldsensing means comprises a first plurality of magnetoresistance elementsand the second plurality of magnetic field sensing elements comprises asecond plurality of magnetoresistance elements, and/or the first andsecond pluralities of magnetoresistance elements comprise one or more ofgiant magnetoresistance (GMR) elements, anisotropic magnetoresistance(AMR) elements, tunneling magnetoresistance (TMR) elements or magnetictunnel junction (MTJ) elements.

In an aspect, a magnetic field sensor integrated circuit comprises: alead frame having a first surface, a second opposing surface, andcomprising a plurality of leads; a substrate having a first surfacesupporting a magnetic field sensing element and a second, opposingsurface attached to the first surface of the lead frame, wherein themagnetic field sensing element is configured to generate a magneticfield signal indicative of movement of a target proximate to theintegrated circuit; a magnet having a first surface and a second,opposing surface, and configured to generate a magnetic field; a spacerpositioned between the first surface of the magnet and the secondsurface of the lead frame and having a thickness selected to establish apredetermined distance between the first surface of the magnet and themagnetic field sensing element, the predetermined distance selected toprovide the magnetic field signal as a sinusoidal signal; and anon-conductive mold material enclosing the substrate, the spacer, andthe magnet, such that at least a portion of at least one of theplurality of leads extends to an exterior surface of the non-conductivemold material.

A magnetic field sensor integrated circuit can further include one ormore of the following features: the thickness of the spacer is furtherselected to provide the magnetic field signal with a predeterminedminimum peak-to-peak signal level, a ratio of the thickness of thespacer to a thickness of the magnet between the first surface of themagnet and the second surface of the magnet is selected to provide themagnetic field signal with the predetermined minimum peak-to-peak signallevel and with less than a predetermined amount of deformation based atleast in part on a nominal expected airgap distance between the magneticfield sensing element and the target and a size of the non-conductivemold material, the spacer is comprised of a material having a magneticpermeability approximately equal to air, the sinusoidal signal has lessthan a predetermined amount of deformation, wherein the predeterminedamount of deformation is based on at least one of a level of harmonicsin the magnetic field signal and a determination of an error curve as adifference between a nominal sinusoidal signal and the magnetic fieldsignal, the spacer has a thickness of approximately 2.4 millimeters, thepredetermined distance between the first surface of the magnet and themagnetic field sensing element is approximately 3.2 mm, the spacercomprises at least one of a copper material or an aluminum material, afirst attachment mechanism disposed between the spacer and the magnet,the first attachment mechanism comprises one or more of a conductive ornon-conductive adhesive, epoxy, tape, film or spray, a second attachmentmechanism disposed between the spacer and the second surface of the leadframe, the second attachment mechanism comprises one or more of aconductive or non-conductive adhesive, epoxy, tape, film or spray, athird attachment mechanism disposed between the second surface of thesubstrate and the first surface of the lead frame, the third attachmentmechanism comprises one or more of a conductive or non-conductiveadhesive, epoxy, tape, film or spray, the substrate comprises asemiconductor die, and/or the magnet comprises a sintered magnet or aferromagnetic element or both.

In another aspect, a magnetic field sensor integrated circuit comprises:a lead frame having a first surface, a second opposing surface, andcomprising a plurality of leads; a substrate having a first surfacesupporting a magnetic field sensing element and a second, opposingsurface attached to the first surface of the lead frame, wherein themagnetic field sensing element is configured to generate a magneticfield signal indicative of movement of a target proximate to theintegrated circuit; a magnet having a first surface and a second,opposing surface, and configured to generate a magnetic field, wherein afirst surface of the magnet is disposed at a predetermined distance fromthe magnetic field sensing element, the predetermined distance selectedto provide the magnetic field signal as a sinusoidal signal; and anon-conductive mold material enclosing the substrate and the magnet,such that at least a portion of at least one of the plurality of leadsextends to an exterior surface of the non-conductive mold material.

A magnetic field sensor integrated circuit can further include one ormore of the following features: a spacer disposed between the firstsurface of the magnet and the second surface of the lead frame andwherein the predetermined distance is established by a thickness of thespacer, the predetermined distance is established by a thickness of thelead frame, and/or the sinusoidal signal has less than a predeterminedamount of deformation.

In a further aspect, a method of generating a magnetic field signalindicative of movement of a target, the method comprising: attaching asubstrate to a first surface of a lead frame comprising a plurality ofleads, the substrate having a first surface supporting a magnetic fieldsensing element configured to generate the magnetic field signalindicative of movement of the target proximate to the magnetic fieldsensing element and a second, opposing surface attached to the firstsurface of the lead frame; spacing a magnet from the magnetic fieldsensing element by a predetermined distance that is selected so that themagnetic field sensing element provides the magnetic field signal as asinusoidal signal; and molding over the substrate and the magnet with anon-conductive mold material.

A method can further include one or more of the following features: thepredetermined distance is selected to provide the magnetic field signalwith a predetermined minimum peak-to-peak signal level, the spacingcomprises: attaching a spacer to the magnet with a first attachmentmechanism comprising one or more of a conductive or non-conductiveadhesive, epoxy, tape, film or spray, and/or attaching the spacer to thesecond surface of the lead frame with a second attachment mechanismcomprising one or more of a conductive or non-conductive adhesive,epoxy, tape, film or spray.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention, as well as the invention itselfmay be more fully understood from the following detailed description ofthe drawings, in which:

FIG. 1 is a schematic representation of a magnetic field sensor havingsensing element bridges having example orientations;

FIG. 2 is a schematic representation of first and second sensing elementbridges positioned in relation to a magnet;

FIG. 3A is a schematic representation of a sensor having a sensingelement bridge and FIG. 3B shows an example circuit connection of thebridge sensing elements;

FIG. 4 is a schematic representation of magnetic sensor IC package in afirst orientation in relation to a rotating target;

FIGS. 4A-4C show flux deflections for respective positions of a rotatinggear tooth target for the sensor orientation of FIG. 4;

FIG. 5 is a schematic representation of a magnetic sensor IC package ina second orientation in relation to a rotating target;

FIGS. 5A-5C show flux deflections for respective distances of a targetfor the sensor orientation of FIG. 5;

FIG. 6 is a circuit diagram showing electrical bridge sensing elementconnections for the sensor orientation of FIG. 5;

FIG. 7 shows an example sequence of steps for providing a magnetic fieldsensor operation at multiple orientations in relation to a target;

FIG. 8 is a block diagram showing layers of an example of amagnetoresistance element having a particular double pinned arrangement;

FIG. 9 is a top view diagram of magnetic field sensing element having ayoke shape that, in some embodiments, can describe a shape of themagnetoresistance element of FIG. 8;

FIG. 10 is a block diagram of a magnetoresistance element magnetic fieldsensor placed above a magnetic target for rotation speed measurement;

FIG. 10A is a schematic representation of a portion of a sensor havingmagnetic field sensing elements and FIG. 10B shows a circuitrepresentation of left and right bridges formed by the magnetic fieldsensing elements of FIG. 10A;

FIG. 11A shows a target having a rectangular gear teeth;

FIG. 11B shows a target having sinusoidal gear teeth;

FIG. 12A is a waveform diagram of sine and cosine signals for a sensorfor the target of FIG. 11A;

FIG. 12B is a waveform diagram of sine and cosine signals for a sensorfor the target of FIG. 11B;

FIG. 13A is a plot of angle error for the target of FIG. 11A;

FIG. 13B is a plot of angle error for the target of FIG. 11B;

FIG. 14 is a plot of angle error versus air gap for the targets of FIGS.11A and 11B;

FIG. 15 shows a side view of a target having a sinusoidal profile withsecond and fourth harmonic reduction;

FIG. 16 is a graphical representation of angle error for the second andfourth harmonics;

FIG. 17 is a plot of sine and cosine signals for amplitude versus airgap;

FIG. 18 is a schematic representation showing the location of bridgeelements and a target;

FIG. 19 is a simplified cross-sectional view of a magnetic field sensorintegrated circuit (IC), according to an embodiment of the presentdisclosure;

FIG. 20A is a top view of a lead frame including ears prior to beingbent that, when bent, provide a spacer between a magnet and a die,according to an embodiment of the present disclosure;

FIG. 20B is a side view of the lead frame of FIG. 20A in a magneticfield sensor assembly;

FIG. 20C is a top view of a lead frame having a thickened portionbetween a magnet and a die to provide a spacer between the magnet andthe die, according to an embodiment of the present disclosure;

FIG. 20D is a side view of the lead frame of FIG. 20C in a magneticfield sensor assembly; and

FIG. 21 is a schematic representation of an example computer that canperform at least a portion of the processing described herein.

DETAILED DESCRIPTION

FIG. 1 shows an example magnetic field sensor 100 having some immunityto common mode fields including field peaks. The sensor 100 includes atleast one bridge 102 for generating sensing signals and canceling outcommon mode fields. In embodiments, the bridge 102 includes magneticfield sensing elements 104 a-d, 106 a-d positioned in relation to a backbias magnet 106, as described more fully below. The magnetic fieldsensing elements 104 and 106 can detect movement of a target 10. Inembodiments, rotational and/or lateral movement of the target 10 can bedetected, as described below.

The bridge 102 has elements 104, 106 electrically connected as shown. Afirst connection to the amplifier 108 is between bridge elements 104 cand 106 d and a second connection to the amplifier is between bridgeelements 104 b and 106 a.

In embodiments, the sensor 100 includes an amplifier 108 to receive theoutput from the bridge 102. The sensor can also include an offsetadjustment module 110 coupled to the bridge output. The amplifier 108output can be digitized with an ADC 112 to provide digital signals to asignal processor 114, which can output a sensor output signal 116.

FIG. 2 shows a portion 200 of a sensor including a magnet 202 having afirst axis of symmetry 204 and a second axis of symmetry 206. In theillustrated embodiment, the first and second axes of symmetry 204, 206lie in the x-z plane. A y-axis is orthogonal to the x-z plane. A die 208is positioned over the magnet 202 and can include magnetic field sensingelements forming a bridge 210 which can correspond to the bridge 102 andbridge elements 104, 106 of FIG. 1. In an example embodiment, the bridge210 comprises magnetic field sensing elements Rm,n,o. In the illustratedembodiments, the elements can be located at a bridge position inrelation to the magnet 202. For example, each element R can beidentified as Rm,n,o, where m indicates a left or right (L or R) bridge,n indicates a left or right position within the particular die or halfdie, and o indicates a top or bottom position (T or B) within thebridge.

As can be seen, the bridge elements 104 a-d, 106 a-d of FIG. 1 are shownwith electrical circuit connections, wherein the bridge elements Rm,n,oof FIG. 2 are shown in a physical location with respect to the magnet202 and axes 202, 204. For example, magnetic field sensing elementR_(RRT) shows the element in the right bridge R on the right side R ofthe right bridge at the top T of the bridge. Magnetic field sensingelement R_(LLB) shows the element in the left bridge L on the left sideL of the left bridge at the bottom B of the bridge.

In an example embodiment, a first distance D1 is centered about thefirst axis of symmetry 204 and is extended from at least one of theinner magnetic field sensing elements R_(LRX) of the bridge 210 to atleast one of the inner magnetic field sensing elements R_(RLX) of thebridge. A second distance D2 is centered about the first axis ofsymmetry 204 and extended from at least one of the outer magnetic fieldsensing elements R_(LLX) of the bridge 210 to at least one of the outermagnetic field sensing elements R_(RRX) of the bridge. In embodiments,the second distance D2 is greater than the first distance D1. In anotherembodiment, the first and second distance D1, D2 are substantiallyequal.

FIG. 3A shows an example sensor 300 having a single bridge configuration302 on a die 304 disposed on a magnet 306. The bridge 302 include a leftL and right R portion and a left side L and a right side R for theparticular left or right portion of the bridge. The elements are shownas R_(LL), R_(LR), R_(RL), R_(RR). FIG. 3B shows the electricalconnections of the bridge elements.

FIG. 4 shows an example magnetic field sensor integrated circuit (IC)package 400 in a first orientation in relation to a rotating structure402 having gear teeth 404. In the illustrated embodiment, the back biasposition of the sensor 400 can be considered the 0 degree position. Theaxis of sensitivity 406 is shown for the sensor IC 400. FIG. 4A shows afirst configuration 440 when field deflection when the gear tooth 404 isat the leading edge in relation to a magnet of the sensor, FIG. 4B showsa second configuration 460 when field deflection when the gear toothcenter is aligned with the magnet, and FIG. 4C shows a thirdconfiguration 480 when the field deflection when the gear tooth is at atrailing edge. In the 0 degree orientation, the magnetic field sensoraxis of sensitivity 406 is along the direction of motion of the geartooth. The sensing elements experience the same signal but with a phaseshift due to different positions along the axis 406.

FIG. 5 shows the magnetic field sensor integrated circuit (IC) package400 in a second orientation in relation to a rotating structure 402having gear teeth 404. The axis of sensitivity 406′ is perpendicular tothe direction of rotation of the target. In the illustrated embodimentof FIG. 5, the back bias position of the sensor 400 can be consideredthe ninety degree position. In this configuration, the sensor is notsensing flux line deflection by the tooth edges, but rather, senses avariation in divergence of the magnetic flux lines coming from the backbias magnet. FIG. 5A shows a first field distribution for a target 50having a surface 52 at a first distance d1 from a magnet 500 of asensor. FIG. 5B shows a second field distribution for the target surface52 at a second distance d2 from the magnet 500. FIG. 5C shows a thirdfield distribution for a target 50 having a surface 52 at a thirddistance d3 from a magnet 500 of a sensor. As can be seen, the exampledark flux lines on the left of FIG. 5A have a different divergence thanthe dark flux lines on the left of FIG. 5C. The divergence variationscan be detected the sensing elements. It is understood that the aboveprovides a target proximity sensor by detecting flux line divergencevariation due to a varying distance of the target from the back biasmagnet. It should be noted that the phase shifts in the 90 degreesorientation are not detected.

In embodiments, the electrical connections of the bridge elements 104a-d, 106 a-d in series shown in FIG. 1 correspond to the 90 degreeorientation of FIG. 5. This arrangement enables the positioned bridgeelements 104, 106 to detect variation in flux line divergence from theback bias magnet.

While example embodiments are shown and described in conjunction withzero and ninety degree orientations, it understood that the respectiveorientations can range from 0 to 360 degrees to meet the needs of aparticular embodiment. It will be appreciated that a 0 degreeorientation and a 180 degree orientation may be equivalent due to thesymmetry of the system. In embodiments, due to the symmetry of thesystem, what works at an orientation angle X also works at angle X+90,−X and −X−90, thus providing a system that operates over a 360 degreerange.

FIG. 6 shows an example circuit connection of bridge elements to recoverdirection sensing in the ninety degree orientation of FIG. 5. It isunderstood that the bridge elements can be physically positioned inrelation to the magnet as shown in FIG. 2. The magnetic field sensingelements are connected so as to recover direction sensing when thesensor is positioned at the 90 degree position for rotating targets. Inthe illustrated embodiment, a first bridge 600 includes magnetic fieldsensing elements R_(LLT), R_(RRT), R_(LRT), R_(RLT) and a second bridge602 includes magnetic field sensing elements R_(LLB), R_(RRB), R_(LRB),R_(RLB). The first and second bridges 600, 602, generate differentialfirst and second signals from which a phase shift can be recovered fordirection sensing.

In embodiments, bridge elements are shared and selectively connected toachieve the example circuit connections shown in FIG. 1 and FIG. 6. Inother embodiments, bridge elements are dedicated to the circuitconfigurations shown in FIG. 1 and FIG. 6.

FIG. 7 shows an example process 700 for providing a magnetic fieldsensor in accordance with example embodiments of the invention. In step702, a magnetic field sensor is positioned relative to a target suchthat an axis of sensitivity of first and second pluralities of magneticfield sensing elements of the magnetic field sensor are rotated at apredetermined angle with respect to an axis of rotation of a target. Instep 704, a first pair of magnetic field sensing elements of the firstplurality of magnetic field sensing elements can be spaced a firstdistance from each other and spacing a second pair of magnetic fieldsensing elements of the second plurality of magnetic field sensingelements a second, different distance from each other. In step 706, afirst magnetic field signal is generated by the first plurality ofmagnetic field sensing elements, wherein the first magnetic fieldstructure is indicative of a position of the target. In step 708, asecond magnetic field signal indicative of the position of the target isgenerated by the second plurality of magnetic field sensing elements. Instep 710, an output signal is generated based on the first magneticfield signal and the second magnetic field signal, wherein the outputsignal corresponds to the position of the target and a change in aproperty of the magnetic field generated by the magnet.

Embodiments of a magnetic field sensor are described that have someimmunity, which can be provided by differential bridge structures tocancel out the common mode. Embodiments of a magnetic field sensor withback bias can sense target direction in a first, e.g., zero degree,orientation, and sense vicinity of a ferromagnetic target in a second,e.g., 90 degree, orientation. In this sensing mode, the sensor is notsensing the flux line deflection by the target in the form of gear toothedges, for example, rather in the second orientation the sensor sensesthe variation of the divergence of the magnetic flux lines coming fromthe back biasing magnet.

In example embodiments, MR elements are used as sensing elements in thebridges to detect flux change. It understood that any suitable magneticfield sensing element can be used to meet the needs of a particularapplication.

In aspects of the invention, embodiments a resolver sensor can obtaintarget angle information using a signal die and target. In otherembodiments, multiple targets and/or multiple sensors can be used forposition encoding. In some embodiments, angle information can beobtained using example sensors, as described above. In otherembodiments, sensors can include a double spin valve stack, as describedbelow.

Referring now to FIG. 8, an example of a double pinned GMR element 800includes a plurality of layers disposed over a substrate, as shown anddescribed in U.S. Patent Publication No. US 2016/0359103, which isincorporated herein by reference. An upper surface of the substrate isshown as a dark line at the bottom of FIG. 8. On the left side of FIG.8, each layer is identified by functional name. On the right side orFIG. 8 are shown magnetic characteristics of sublayers that can form thefunctional layers.

Examples of thicknesses of the layers of the GMR element 800 are shownin nanometers. Examples of materials of the layers of the GMR element800 are shown by atomic symbols. The exemplary GMR element 800 caninclude a seed layer 802 disposed over the substrate, anantiferromagnetic pinning layer 804 disposed over the seed layer 802,and a pinned layer 806 disposed over the antiferromagnetic pinning layer804. However, in some embodiments, the pinned layer 806 can be comprisedof a first ferromagnetic pinned layer 806 a, a second ferromagneticpinned layer 806 c, and a spacer layer 806 b disposed therebetween. Insome embodiments, the spacer layer 806 b is comprised of a nonmagneticmaterial. In some other embodiments, the pinned layer 806 can instead becomprised of one pinned layer.

Due to the presence of the spacer 806 b between the first and secondferromagnetic pinned layers 806 a, 806 c, the second ferromagneticpinned layer 806 c tends to couple antiferromagnetically with the firstferromagnetic pinned layer 806 a, and thus, it has a magnetic fieldpointing in the other direction, here shown pointing to the right. Asdescribed above, the combination of the three layers 806 a, 806 b, 806 ccan be referred to as a synthetic antiferromagnetic structure or layer.

The exemplary GMR element 800 can also include a spacer layer 808disposed over the second ferromagnetic pinned layer 806 c, and a freelayer 810 disposed over the spacer layer 808. In some embodiments, thefree layer 810 can be comprised of a first ferromagnetic free layer 810a disposed under a second ferromagnetic free layer 810 b. In someembodiments, the spacer layer 808 is comprised of a nonmagnetic material(e.g., conductive Cu for GMR or an insulating material for TMR).

The GMR element 800 of FIG. 8 can further include a spacer layer 812disposed over the second ferromagnetic free layer 810 b, and a secondpinned layer 814 disposed over the spacer layer 812. In someembodiments, the second pinned layer 814 can be comprised of aferromagnetic material. In some embodiments, the spacer layer 812 iscomprised of a nonmagnetic material (e.g., Ru). The GMR element 800 ofFIG. 8 can further include a second antiferromagnetic pinning layer 816disposed over the second pinned layer 814. A cap layer 818 can bedisposed at the top of the GMR element 800 to protect the GMR element800. Within some layers, arrows are shown that are indicative ordirections of magnetic fields of the layers when the GMR element 800does not experience an external magnetic field. Arrows coming out of thepage are indicated as dots within circles and arrows going into the pageare indicated as crosses within circles.

In some embodiments, the seed layer 802 is comprised of Ru or Ta, andthe first antiferromagnetic pinning layer 804 is comprised of PtMn. Insome embodiments, the first pinned layer 806 is comprised of the firstferromagnetic pinned layer 806 a comprised of CoFe, the spacer layer 806b comprised of Ru, and the second ferromagnetic pinned layer 806 ccomprised of CoFe. In some embodiments, the spacer layer 808 iscomprised of Cu (or alternatively, Au, or Ag). In some embodiments, thefirst ferromagnetic free layer 810 a is comprised of CoFe and the secondferromagnetic free layer 810 b is comprised of NiFe. In someembodiments, the spacer layer 812 is comprised of Ru (or alternatively,Au, or Ag), the second pinned layer 814 is comprised of CoFe, the secondantiferromagnetic pinning layer 816 is comprised of PtMn, and the caplayer 818 is comprised of Ta. However, other materials are alsopossible.

The spacer layer 812 being comprised of Ru (or Au, or Ag) allowsrealizable ranges of thicknesses (described below) of the spacer layer812 to allow for partial pinning of the free layer 810. Partial pinningis described more fully below.

In some other embodiments, the first and second antiferromagneticpinning layers 804 and 816 can be comprised of IrMn, FeMn, or any othertype of antiferromagnetic material. PtMn or IrMn are shown in thefigure, and PtMn is used in examples below. In some other embodiments,the second pinned layer 814 can instead be comprised of a plurality ofsublayers, the same as or similar to the sublayers of the first pinnedlayer 806. In some other embodiments, the spacer layer 808 can becomprised of Ta or Cu.

A thickness of the spacer layer 812 is selected to provide a desiredamount of (i.e., a partial) magnetic coupling between the second pinnedlayer 814 and the free layer 810. Also, the thickness of the spacerlayer 812 is selected to provide a desired type of magnetic couplingbetween the second pinned layer 814 and the free layer 810, i.e.,ferromagnetic coupling or antiferromagnetic coupling, or betweenferromagnetic and antiferromagnetic coupling. Here, the coupling isshown to be ferromagnetic coupling, but, by selection of the thicknessof the spacer layer 812, the coupling can be antiferromagnetic orbetween ferromagnetic and antiferromagnetic coupling. In other words, inthe absence of an external magnetic field it is possible for a directionof magnetic fields of the free layers 810 to be rotated either as shown(out of the page) or into the page, depending upon a selected thicknessof the spacer layer 812.

Taking CoFe and NiFe to have similar magnetic properties, it will berecognized that the layers of materials above the first ferromagneticfree layer 810 a and below the first ferromagnetic free layer 810 a aresimilar, but in reversed order, namely, NiFe (or CoFe)/Ru/CoFe/PtMn.However, it is desired that the spacer layer 806 b provides highcoupling between surrounding layers, thus it is thin, while it isdesired that the spacer layer 812 provide less coupling betweensurrounding layers, thus it is thicker.

Ru is well suited for the spacer layer 812 because it allowsantiferromagnetic or ferromagnetic coupling (also called Ruderman KittelKasuya Yoshida or RKKY coupling) between surrounding layers, accordingto the Ru thickness. In essence, the Ru material permits couplingthrough it, as opposed to in spite of it. This allows for a thicker Rulayer 812, with a range of achievable thickness values, to achieve andto tune the desired partial pinning of the free layer 810.

In some embodiments, the thickness of the Ru spacer layer 812 isselected to provide an RKKY coupling of between about −50 mT and about50 mT. The RKKY coupling tends to be stable with respect to possibleprocess drift, i.e., the amount of coupling tends to remain constant andstable even for a thickness change of about ten percent in the Ru layerdue to manufacturing process variations or the like.

The second pinned layer 814, having a pinned magnetic field pointingdirection aligned with a pointing direction of the magnetic field in thefree layer 810, tends to cause particular behavior within the free layer810. In particular, the pointing direction of the magnetic field in thesecond pinned layer 814 causes a reduction in the number of magneticdomains in the free layer 810 that point at directions other than thedirection of the net magnetic field of the free layer, i.e., a reductionin the number of magnetic domains that point in directions other thanout of the page when in the presence of no external magnetic field.

The ferromagnetic free layers 810 a, 810 b tend to naturally have aplurality of magnetic domains, including, but not limited to, a firstplurality of magnetic domains with magnetic fields pointing in a firstdirection and a second plurality of magnetic domains with magneticfields pointing in one or more directions different than the firstdirection. The first direction described above can be parallel to upperand lower surfaces of the free layer 810. The first plurality ofmagnetic domains have magnetic field pointing directions that arealigned with the net magnetic field of the free layer 810 shown to becoming out of the page when the GMR element 800 is not exposed to anexternal magnetic field, but which can rotate as the GMR element 800 isexposed to a magnetic field. As described above, the magnetic fieldpointing direction of the first plurality of magnetic domains in thefree layer 810 rotates in response to an external magnetic field. Thesecond plurality of magnetic domains will tend to have magnetic fieldpointing directions that point in the one or more directions differentthan the first direction.

The second pinned layer 814 is operable to partially magneticallycouple, through the spacer layer 812, to the free layer 810, to reduce anumber of magnetic domains (i.e., to reduce a quantity of magneticdomains in the second plurality of magnetic domains) in the free layer810 that point in a direction other than the first direction, i.e.,other than the direction of the net magnetic field in the free layer 810in the absence of an external magnetic field.

By partial pinning, it is meant that there is less magnetic couplingbetween the second pinned layer 814 and the free layer 810 than betweenthe first pinned layer 806 and the free layer 810. An amount of partialpinning is determined in part by a material and a thickness of thespacer layer 812.

The PtMn first and second antiferromagnetic pinning layer 804, 816 canhave a Neel temperature and a blocking temperature that are both aboveabout three hundred degrees Celsius. This high temperature is importantto eliminate loss of magnetic characteristics of the GMR element 800 inhigh temperature applications, for example, automobile applications.

While the layers of the GMR element are shown in a particular order, itshould be understood that, in other embodiments, the layers 804, 806(i.e., 806 a, 806 b, 806 c), and 808 can be exchanged with the layers816, 814, 812, respectively. In some embodiments, all of the layersshown in FIG. 8, except for the seed layer and the cap layer, can bereversed in order from bottom to top.

For a GMR element, the spacer layer 808 is a metallic nonmagnetic layer(usually Copper). For a TMR element, the spacer layer 808 is aninsulating nonmagnetic layer (e.g., Al2O3 or MgO). Otherwise, the GMRelement 800 can have layers the same as or similar to a comparable TMRelement. Thus, a TMR element is not explicitly shown.

Referring now to FIG. 9, in which like elements of FIG. 8 are shownhaving like reference designations, according to a specific embodiment,the magnetoresistance element 800 of FIG. 8, and also magnetoresistanceelements, can be formed in the shape of a yoke 900.

The yoke 900 has a main part 901, two arms 906, 908 coupled to the mainpart 901, and two lateral arms 912, 914 coupled to the two arms 906,908, respectively. In some embodiments, the main part 901, the two arms906, 908, and the two lateral arms 912, 914 each have a width (w).However, in other embodiments, the widths can be different.

A length (L) of the yoke 900 and a length (d) of the lateral arms 912,914 of the yoke 900 are each at least three times the width (w) of theyoke 900, and the width (w) of the yoke 900 can be between about one μmand about twenty μm.

The yoke dimensions can be, for example, within the following ranges:

-   -   the length (L) of the main part 901 of the yoke 900 can be        between about ten μm and ten millimeters;    -   the length (l) of the arms 906, 908 of the yoke 900 can be at        least three times the width (w);    -   the width (w) of the yoke 900 can be between about one μm and        about twenty μm.

The arms 906, 908 of the yoke 900 are linked to the lateral arms 912,914, which are parallel to the main part 901, and have a length l whichis between about ¼ and ⅓ of the overall length (L).

In general, sensitivity of the magnetoresistance element 800 having theyoke shape 900 decreases with the width (w), and the low frequency noiseof the magnetoresistance element 800 increases with the width (w).

The yoke shape offers better magnetic homogeneity in a longitudinallycentral area of the main part 901. This is due to the demagnetizingfield of the yoke length which is mainly along the main part 901, andthis induces an anisotropy of the free layer 810 of FIG. 8, which can beseen as a magnetization at zero field along the length of the yoke 900.If the pinned layer (e.g., 806 of FIG. 8) has a magnetic fieldperpendicular to the yoke (e.g., arrow 902), when an external field isapplied in direction of the arrow 902, the free layer 810 magnetizationrotates uniformly, i.e. without domain jumps.

For a GMR element, the overall stack can be designed in a yoke shape,but for a TMR element, in some embodiments, only the free layer can havea yoke shape. In other embodiments, the GMR or TMR elements 800 is notformed in the shape of a yoke, but is instead formed in the shape of astraight bar, e.g., having the dimensions L and w, and not havingfeatures associated with the dimensions l and d. For the bar shaped GMRor TMR element, still the section line A-A is representative of thecross sections of the GMR element 800 of FIG. 8.

Referring now to FIG. 10, a magnetic field sensor 1000 can include oneor more magnetoresistance elements. Here, four magnetoresistanceelements, which can be of a type described above in conjunction withFIG. 8. The four magnetoresistance elements can be arranged in a bridge.Other electronic components (not shown), for example, amplifiers andprocessors, i.e., an electronic circuit, can also be integrated upon thecommon substrate. In some embodiments, the electronic circuit cangenerate an output signal indicative of a movement, e.g., a rotation, ofan object. e.g., 1002.

A surrounding package (not shown) e.g., a plastic package, can surroundor otherwise be included with the magnetic field sensor 1000. Also, aleadframe (not shown) can be coupled to or otherwise be included withthe magnetic field sensor 1000.

The magnetic field sensor 1000 can be disposed proximate to a movingmagnetic object, for example, a ring magnet 1002 having alternatingnorth and south magnetic poles. The ring magnet 1002 is subject torotation.

The magnetic field sensor 1000 can be configured to generate an outputsignal indicative of at least a speed of rotation of the ring magnet. Insome arrangements, the ring magnet 1002 is coupled to a target object,for example, a cam shaft in an engine, and the sensed speed of rotationof the ring magnet 1002 is indicative of a speed of rotation of thetarget object.

As noted above, example sensors such as those described above, e.g.,back-bias sensors and double spin valve stack configurations in whichthe bias of the spin valve plays the role of the bias generated by themagnet, can be used to obtain angle information. In some embodiments, aspin valve configuration may be less sensitive to stray fields and asingle yoke instead of a split yoke.

In aspects, a magnetic field sensor includes hack biasing to obtainangular position with respect to a die and target. In some embodiments,a single die is used. In some embodiments, encoding requires first andsecond targets and first and second sensors. In embodiments, a targethas selected shapes for back bias resolver applications that reduceangular error for the sensor as compared with conventional sensors. Inembodiments, a target is shaped to reduce harmonics, and thereby, reduceangular error.

Referring again to FIGS. 2, 3A, 3B, a ‘left’ bridge and a ‘right’ bridgeare shown. For example, FIG. 2 shows a first bridge 210, which can beconsidered a left bridge, and a second bridge 212, which can beconsidered a right bridge. In example embodiments, the left bridge 210output and the right bridge 212 output are provided to a signalprocessing module, which outputs a target angle signal. It is understoodthat left and right are relative and example terms that are not to beconstrued as limiting in any way. In example embodiments, left and rightbridges include an element from the bridge center as shown in thisfigure and the sensor should be at a zero degree orientation.

For example, FIG. 10A shows a sensor having GMR elements and FIG. 10Bshows an alternative bridge construction in which GMR elements aresubject to opposite bias. FIG. 10A shows first and second GMR bridgeseach having four elements where each element has first and secondsegments. Output signals in the left and right bridges can be used todetermine speed and direction information. In one embodiment,subtraction and sum of signals in the left and right bridges outputsspeed and direction information. In some embodiments, sine and cosineinformation can be generated, as described more fully below. The GMRelements are labeled such that subscription 1 refers to left, r refersto right, and c refers to center. Looking to FIG. 10A, yokes Ax and Cxmay be referred to an outer yoke Bx may be referred to as central orinner yokes. From left to right in FIG. 10A, the GMR elements are listedas A_(l), A_(c), B_(l), B_(cl), B_(cry), B_(r), C_(c), C_(r). As seen inthe left bridge of FIG. 10B, GMR element A_(l) includes first and secondsegments A_(la), A_(lb), the GMR element B_(cl) includes third andfourth elements B_(cla), B_(clb), and so on.

In this arrangement, the segments of the GMR elements do not experiencethe exact same bias conditions. This is why the vertical spacing betweentop and bottom pieces of GMR is not the same for outer elements andinner elements. This compensates for this sensitivity issue and maybring back stray field immunity. For example, the bias field, which canbe generated by a magnet, along Y axis (FIG. 10A) varies slightlybetween inner and outer yoke. This produces a difference in sensitivityof the elements, resulting in a global sensitivity to common mode field.

In an example embodiment, left bridge 210 output (Left) and the rightbridge 212 output (Right) are combined to generate sine and cosinesignals as follows:Sine=Left−RightCosine=Left+Right

Once these signals are normalized, the following operation leads to themeasurement of the angle φ of the target within a period of this sametarget:

$\varphi = {\tan^{- 1}\left( \frac{Sine}{Cosine} \right)}$

U.S. Pat. No. 7,714,570, which is incorporated herein by reference,discloses an angle sensor utilizing arc tangent of sine and cosineinformation to generate angular position information.

FIG. 11A shows a first target 1100, which can have some similarity withthe target 402 in FIG. 4, having a first shape and FIG. 11B shows asecond target 1102 having a second shape. As described more fully below,shapes of the first and second targets 1100, 1102 facilitate resolvingtarget angle.

The first target 1100 comprises a target having substantially squareteeth 1110. In an example embodiment, square refers to a given toothhaving a substantially cylindrical outer face 1112 with sides that aresubstantially radial, such as can be seen in FIG. 4.

The second target 1102 has sinusoidal teeth 1120. In an exampleembodiment, a profile of the second target 1102 is defined as follows:

${R(\theta)} = {R_{0} + {\frac{\delta\; R}{2} \times \left\lbrack {1 - {\cos\left( {n\;\theta} \right)}} \right\rbrack}}$where:R₀ is the outer radius of the targetδR is the valley depthn is the number of teethθ is the angle of the target in a range of 0 degrees to 360 degrees.

FIG. 12A shows illustrative sine and cosine signals 1220 a,b obtainedfrom an example sensor positioned in relation to a square tooth target,such as the first target 1100 of FIG. 11A. The target 1100 has nineteeth and has a 1 mm air gap with the sensor IC. FIG. 13A shows exampleangle error for the first target 1100 of FIG. 11A.

FIG. 12B shows illustrative sine and cosine signals 1230 a,b obtainedfrom an example sensor positioned in relation to a sinusoidal profiletarget, such as the second target 1102 of FIG. 12B. FIG. 13B show anillustrative angular error obtained for a nine teeth target having asinusoidal profile.

As can be seen in FIG. 14, the sine tooth target 1102 (FIG. 11B)generates a lower angular error than the square tooth target 1100. Itcan also be seen that the higher the air gap, the better the angularerror for the sine tooth target. It should be noted that the air gapwith the sensor should be small to maximize signal.

The angular error shown on FIG. 13B shows that the error figure followsa harmonic distribution.

FIG. 15 shows an example target 1500 having a profile that includesharmonics so as to reduce angular error. An example target profile canbe defined as:

${R(\theta)} = {R_{0} + {\sum\limits_{h = 0}^{N}{\frac{\delta\; R_{h}}{2} \times \left\lbrack {1 - {\cos\left( {{n\left( {h + 1} \right)}\theta} \right)}} \right\rbrack}} - {\max\left( {\sum\limits_{h = 0}^{N}{\frac{\delta\; R_{h}}{2} \times \left\lbrack {1 - {\cos\left( {{n\left( {h + 1} \right)}\theta} \right)}} \right\rbrack}} \right)}}$R₀ is the outer radius of the targetδR is the valley depthn is the number of teethθ is the angleh is the harmonic index.Rh is the amplitude of the h-th harmonic.

It is understood that selecting the number of harmonics corresponds tothe number of shapes that can be provided, as well as the improvement inharmonic reduction. FIG. 15 is an example with a given number ofharmonics (1^(st), 2^(nd) and 4^(th)).

In some embodiments, first and second harmonics are used to generate atarget with 1^(st) and 2^(nd) harmonic profiles combined. One cancalculate the angle error for different harmonic amplitudes (meaningharmonic profile radii) and plot a graph similar to FIG. 16 but with1^(st) harmonic amplitude in X, 2^(nd) harmonic amplitude in Y, andangle error in color scale. Then one can select the conditions at whichthe angle error is at a minimum.

In some embodiments, the use of a sinusoidal profile may make it easierto see that the angle error is composed of harmonic components. If thetarget profile can be described with one single sine (e.g., FIG. 11B),then the angle error will have a profile that is a combination of thissinus with the given period. It is understood that a square profile(e.g., FIG. 11A) can be decomposed in a sum of an infinity of sineharmonics of the fundamental period. Then the angle error is acombination of harmonics of all these harmonics.

It should be noted that with sinusoidal functions, one can reproduce anyshape of tooth for a relatively large number of harmonics. It will beappreciated that as the error is harmonic it may be faster to determinea ‘good’ correction by tuning the a of the dominant harmonic of theerror.

FIG. 16 shows the effect of adding second and fourth harmonics to atarget profile. As can be seen, it shows the maximum angular error overa period for different values of the amplitude of the second and fourthharmonics R₂ and R₄. By tuning these harmonics, the maximum error isreduced by a factor of about three. It is understood that FIG. 16provides a tool to facilitate determining a profile for a target. Forexample, error minimization can be run over harmonics amplitude todetermine a target profile, such as the profile of the target in FIG.15. It is understood that the target shape, such as the target of FIG.15, depends on the magnet shape, the distance between the magnet and thedie and the distance between the die and the target.

In addition, example embodiments of the sensor can obtain relativelysimilar amplitudes on the sine and cosine waveforms. FIG. 17 shows howthe amplitude of the sine and cosine waveforms vary with air gap. As canbe seen, at about 1 mm air gap, the amplitude of the sine and cosinesignals is the same. This crossover air gap can be selected by adjustingthe target period length in relation with the element spacing on thedie, for example. The target period corresponds to a certain length onthe die, which is the target period length. To obtain the same amplitudeon sine and cosine, then the left and right bridges centers should bedistant from each other by 90°, meaning ¼ of the target period length.

To obtain sine and cosine of the same amplitude, a 90° phase shift isimplemented between the left and right bridge outputs. The orthogonalitycomes from the mathematics of adding and subtracting phase shiftedsinusoidal signals. The 90° phase shift is determined from trigonometricrelationships in a manner similar to obtaining the same amplitude onsine and cosine. For example, assume left bridge varies as cos(wt+phi)and right bridge varies as cos wt−phi) where w is the pulsation, t isthe time and phi is the phase shift between the left and right bridges.Then:Left+right=cos(phi)cos(wt)Left−right=sin(phi)sin(wt)

Orthogonality is provided as the sum provides cos(wt) and thesubtraction provides sin(wt). Also to get the same amplitude we needcos(phi)=sin(phi), therefore phi=45°.

In an example embodiment, and shown in FIG. 18, the system can bedefined in accordance with the following equation:

$\frac{BS}{2\left( {{TR} + {AG}} \right)} = {\tan\left( \frac{90^{{^\circ}}}{2n} \right)}$

-   -   where:        BS is the distance between the centers of left and right bridges        TR is the outer radius of the target        AG is the air gap        n is the number of periods in the target

In another aspect, a magnetic resolver sensor includes a spacer toposition a magnet a selected distance from the sensing element. Theselected distance should provide sufficient flux to obtain good signalquality and ensure that the sensing signal is sinusoidal. The distanceshould also avoid excessive influence on the signal from the surfacetopology of what is being sensed while ensuring that airgap changes havereduced impact on the amount of absolute field offset to the dynamicresponse.

Referring to FIG. 19, a simplified cross-sectional view of a magneticfield sensor 1900 is shown, implemented as an integrated circuit (IC)1910. The sensor integrated circuit (IC) 1910 includes a lead frame 1920comprising a plurality of leads, a substrate 1930 attached to the leadframe 1920, a magnet 1950, and a spacer 1940 positioned between the leadframe 1920 and the magnet 1950. The substrate 1930 can be anyappropriate structure and material to support at least a magnetic fieldsensing element 1932, such as a semiconductor die. At least a portion ofthe lead frame 1920 extends exterior of the IC package 1910 to permitconnections (e.g., supply voltage, ground, and/or output connections) tothe IC package 1910.

A dashed-line box represents the IC package 1910, for example as may beformed by over-molding with a non-conductive mold material, with only aportion of the lead frame 1920 accessible from exterior of the ICpackage 1910. For example, the package 1910 can be comprised of anon-conductive mold material formed to enclose the semiconductor die1930, the spacer 1940, the magnet 1950, and a portion of the lead frame1920. The die 1930 can comprise a substrate having a first surface 1930a supporting at least a magnetic field sensing element 1932 and asecond, opposing surface 1930 b attached to the lead frame 1920.Electrical Connections (e.g., as may take the form of wire bonds) can beprovided between the die 1930 and the lead frame 1920 within the moldedpackage 1910.

The magnet 1950 is configured to generate a magnetic field and themagnetic field sensing element 1932 is configured to generate a magneticfield signal indicative of movement of a target object (not shown)proximate to the IC package 1910. The magnet 1950 may be comprised of ahard ferromagnetic or simply hard magnetic material (i.e., a permanentmagnet such as a segmented ring magnet) to form a back bias magnet andmay be formed by sintering or molding for example.

The spacer 1940 is positioned between the magnet 1950 and the lead frame1920 and in particular is attached to a surface of the lead frame 1920opposite the surface to which the die 1930 is attached, as shown. Thethickness of the spacer 1940 is selected to establish a predetermineddistance between the magnet and the magnetic field sensing element.Further, by providing an integrated circuit package 1910 enclosed by anon-conductive mold material, the placement of the magnet 1950, thespacer 1940, and the substrate 1930 with respect to each other isprecise and fixed.

The predetermined distance between the magnet 1950 and the magneticfield sensing element 1932 can be selected to provide the magnetic fieldsignal as a sinusoidal signal. It will be appreciated that decreasingthe predetermined distance too much (i.e., making the magnet and themagnetic field sensing element too close to each other) can result indeformation of the sinusoidal signal, while increasing the predetermineddistance too much (i.e., providing the magnet and the magnetic fieldsensing element too far apart) can result in a weak magnetic fieldsignal that can be difficult to detect and process accurately. Forexample, if the magnet 1950 and magnetic field sensing element 1932 aretoo close to each other and the target is a square-tooth gear, and issufficiently close to the sensor, then the signal will start to track asquare shape, significantly deformed from the sinusoidal. Thus, thepredetermined distance is selected to achieve a sufficiently strongmagnetic field signal, however without deforming the sinusoidality(i.e., the extent to which the signal follows a nominal sinusoidalfunction) of the magnetic field signal or at least with less than apredetermined amount of deformation. The target shape can be taken intoaccount to still further reduce the deformation and/or improve thequality of the sinusoidal signal.

The thickness of the spacer 1940, and thereby the predetermined distancebetween the magnetic field sensing element 1932 and the magnet 1950, isselected to provide the magnetic field signal as a sinusoidal signalhaving less than a predetermined amount of deformation and/or having apredetermined minimum peak-to-peak signal level. The amount ofdeformation can be determined by determining the Fourier transform ofthe magnetic field signal and the resulting harmonic coefficients.Another way to determine the amount of deformation of the magnetic fieldsignal is to generate an error curve by comparing and taking differencevalues between a predetermined nominal sinusoidal signal and themeasured magnetic field signal and considering the maximum error (i.e.,the largest deviation) between the signals. It will be appreciated thatvarious factors affect the tradeoff between deformation of the magneticfield signal from a “perfect” sinusoid and signal strength. Optimizationof these conflicting requirements can be achieved by sizing the spacer1940 so that a ratio of the thickness of the spacer to a thickness ofthe magnet can be selected to provide the magnetic field signal with apredetermined minimum peak-to-peak signal level and/or with less than apredetermined amount of deformation for a given package size and airgap(i.e., nominal distance between the magnetic field sensing element 32and the target). In other words, once the maximum combined thickness ofthe magnet 1950 and spacer 1940 is determined based on the size of theIC package 1910 for the given application, the ratio of spacer thicknessto magnet thickness is selected to achieve the desired magnetic fieldsignal level and deformation results.

The spacer 1940 can be comprised of a material having a magneticpermeability approximately equal to air. For example, the spacer 1940can be a copper material or aluminum material, or any other materialhaving a magnetic permeability approximately equal to air. In an exampleembodiment, the spacer can have a thickness of approximately 2.4millimeters (mm), and the predetermined distance between the magnet andthe magnetic field sensing element is approximately 3.2 mm.

In some embodiments, a first attachment mechanism 1922 can be disposedbetween the spacer 1940 and the magnet 1950, a second attachmentmechanism 1924 can be disposed between the spacer 1940 and the leadframe 1920, and a third attachment mechanism 1926 can be disposedbetween the die 1930 and the lead frame 1920. The first, second, andthird attachment mechanisms 1922, 1924, 1926 can comprise one or more ofa conductive or non-conductive adhesive, epoxy, a tape, a film, a spray,or solder. Any other form of mechanical attachment can be provided.

FIG. 20A is a top view of an alternative lead frame 2020 including ears2010, 2012 prior to being bent that, when bent, provide a spacer betweena magnet and a die for use in a further magnetic field sensor ICembodiment.

Lead frame 2020 can include a die attach portion 2021 to support asubstrate (shown in FIG. 20B). Lead frame ears 2010, 2012 can each havea first portion 2022, 2023 extending from the die attach portion 2021 oflead frame 2020 and a second portion 2024, 2026 extending, respectively,from the first portion. Note that each of the ears 2010, 2012 canfurther include a third portion 2027, 2028 (shown in dotted line) tofurther support the magnet. As shown in FIG. 20B, the ears 2010 and 2012can be bent to form a spacer 2034 between the die attach portion 2021 ofthe lead frame 2020 (and, thus, the die 2030) and the magnet 2011.

The lead frame 2020 can comprise a plurality of leads 2040, 2042, 2044,2046, with at least one of the leads (lead 2046 in this embodiment)directly connected to the die attach portion 2021 of lead frame 2020.One or more other leads 2040, 2042, 2044 can be coupled to the die withwire bonds (not shown). In some embodiments, a different lead, more thanone lead, or all of the leads may be directly connected to the dieattach portion 2021.

FIG. 20B is an end view of the lead frame 2020 and of FIG. 20A inassembly with a die 2030 and magnet 2011, as taken along line 20B-20B ofFIG. 20A (after the ears of the lead frame have been bent to form thespacer). The spacer 2034 formed between the magnet 2011 and the die 2030can comprise air or may be filled with a suitable material having apermeability greater than or equal to that of air.

To arrive at the structure of FIG. 20B, the ears 2010, 2012 of the leadframe 2020 are bent at both ends of first portion 2022, 2023, and thenthe magnet 2011 can be placed on the second portions 2024, 2026 of ears2010, 2012 to form spacer 2034. The die 2030, although not shown in FIG.20A, may be positioned on the side of the lead frame 2020 opposite themagnet, as shown in FIG. 20B. It will be appreciated that the spacer2034 establishes a predetermined distance between the magnet 2011 andthe die 2030 (and more specifically, the sensor on the die 2030), whichpredetermined distance can be selected to provide the magnetic fieldsignal as a sinusoidal signal, as explained in connection with FIG. 19above. More specifically, the length of the first portion 2022, 2023 ofrespective ears 2012, 2010 establishes the distance between the die 2030and magnet 2011, as shown.

FIG. 20C is a top view of a further alternative lead frame 2020′ havinga thickened portion between a magnet 2011′ and a die 2030′ to therebyprovide a spacer between the magnet and the die, according to a furtherembodiment. The lead frame 2020′ has a magnet 2011′ attached to a firstsurface and a die 2030′ (i.e., substrate that supports a magnetic fieldsensing element) attached to a second, opposing surface (shown indotted-line in FIG. 20C, as it is positioned underneath the lead frame2020′).

The lead frame 2020′ can comprise a plurality of leads 2040, 2042, 2044,and 2046, with at least one of the leads (lead 2046 in this embodiment)directly connected to a die attach portion of the lead frame 2020′. Oneor more other leads 2040, 2042, 2044 may be coupled to the die with wirebonds (not shown). In some embodiments, a different lead, more than onelead, or all of the leads may be directly connected to the lead frame2020′.

FIG. 20D is a side view of the lead frame and die assembly of FIG. 20C,as taken along line 20D-20D of FIG. 20C. The lead frame 2020′ supportsthe magnet 2011′ on a first surface and the die 2030′ on a second,opposing surface. Lead frame 2020′ can have a thickened portion betweenthe magnet 2011′ and the die 2030′ to provide the necessary distance(2005) between the magnet 2011′ and the die 2030′, according to anembodiment of the present disclosure. It will be appreciated that thethickness 2005 of the lead frame 2020′ provides a specific predetermineddistance between the magnet 2011′ and the die 2030′ (and, morespecifically, between the magnet 2011′ and the magnetic field sensingelement on the die 2030′), which predetermined distance can be selectedto provide the magnetic field signal as a sinusoidal signal, asexplained in connection with FIG. 19 above.

The lead frame 2020′ and die 2030′ may be formed as part of an ICpackage in which the die 2030′, magnet 2011′, and a portion of the leadframe 2020′ are enclosed by a non-conductive mold material 2013. Leads2040, 2042, 2044, 2046 can comprise a thinner portion 2015 (external tothe package) to allow for the leads 2040, 2042, 2044, 2046 to be bentwith respect to the package 2017, as shown by arrow 2019.

FIG. 21 shows an exemplary computer 2100 that can perform at least partof the processing described herein. The computer 2100 includes aprocessor 2102, a volatile memory 2104, a non-volatile memory 2106(e.g., hard disk), an output device 2107 and a graphical user interface(GUI) 2108 (e.g., a mouse, a keyboard, a display, for example). Thenon-volatile memory 2106 stores computer instructions 2112, an operatingsystem 2116 and data 2118. In one example, the computer instructions2112 are executed by the processor 2102 out of volatile memory 2104. Inone embodiment, an article 2120 comprises non-transitorycomputer-readable instructions.

Processing may be implemented in hardware, software, or a combination ofthe two. Processing may be implemented in computer programs executed onprogrammable computers/machines that each includes a processor, astorage medium or other article of manufacture that is readable by theprocessor (including volatile and non-volatile memory and/or storageelements), at least one input device, and one or more output devices.Program code may be applied to data entered using an input device toperform processing and to generate output information.

The system can perform processing, at least in part, via a computerprogram product, (e.g., in a machine-readable storage device), forexecution by, or to control the operation of, data processing apparatus(e.g., a programmable processor, a computer, or multiple computers).Each such program may be implemented in a high level procedural orobject-oriented programming language to communicate with a computersystem. However, the programs may be implemented in assembly or machinelanguage. The language may be a compiled or an interpreted language andit may be deployed in any form, including as a stand-alone program or asa module, component, subroutine, or other unit suitable for use in acomputing environment. A computer program may be deployed to be executedon one computer or on multiple computers at one site or distributedacross multiple sites and interconnected by a communication network. Acomputer program may be stored on a storage medium or device (e.g.,CD-ROM, hard disk, or magnetic diskette) that is readable by a generalor special purpose programmable computer for configuring and operatingthe computer when the storage medium or device is read by the computer.Processing may also be implemented as a machine-readable storage medium,configured with a computer program, where upon execution, instructionsin the computer program cause the computer to operate.

Processing may be performed by one or more programmable processorsexecuting one or more computer programs to perform the functions of thesystem. All or part of the system may be implemented as, special purposelogic circuitry (e.g., an FPGA (field programmable gate array) and/or anASIC (application-specific integrated circuit)).

As used herein, the term “magnetic field sensing element” is used todescribe a variety of electronic elements that can sense a magneticfield. The magnetic field sensing element can be, but is not limited to,a Hall effect element, a magnetoresistance element, or amagnetotransistor. As is known, there are different types of Hall effectelements, for example, a planar Hall element, a vertical Hall element,and a Circular Vertical Hall (CVH) element. As is also known, there aredifferent types of magnetoresistance elements, for example, asemiconductor magnetoresistance element such as Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, for example, a spinvalve, an anisotropic magnetoresistance element (AMR), a tunnelingmagnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).The magnetic field sensing element may be a single element or,alternatively, may include two or more magnetic field sensing elementsarranged in various configurations, e.g., a half bridge or full(Wheatstone) bridge. Depending on the device type and other applicationrequirements, the magnetic field sensing element may be a device made ofa type IV semiconductor material such as Silicon (Si) or Germanium (Ge),or a type III-V semiconductor material like Gallium-Arsenide (GaAs) oran Indium compound, e.g., Indium-Antimonide (InSb).

As is known, some of the above-described magnetic field sensing elementstend to have an axis of maximum sensitivity parallel to a substrate thatsupports the magnetic field sensing element, and others of theabove-described magnetic field sensing elements tend to have an axis ofmaximum sensitivity perpendicular to a substrate that supports themagnetic field sensing element. In particular, planar Hall elements tendto have axes of sensitivity perpendicular to a substrate, while metalbased or metallic magnetoresistance elements (e.g., GMR, TMR, MTJ, AMR)and vertical Hall elements tend to have axes of sensitivity parallel toa substrate.

As used herein, the term “magnetic field sensor” is used to describe acircuit that uses a magnetic field sensing element, generally incombination with other circuits. Magnetic field sensors are used in avariety of applications, including, but not limited to, an angle sensorthat senses an angle of a direction of a magnetic field, a currentsensor that senses a magnetic field generated by a current carried by acurrent-carrying conductor, a magnetic switch that senses the proximityof a ferromagnetic object, a rotation detector that senses passingferromagnetic articles, for example, magnetic domains of a ring magnetor a ferromagnetic target (e.g., gear teeth) where the magnetic fieldsensor is used in combination with a back-biased or other magnet, and amagnetic field sensor that senses a magnetic field density of a magneticfield.

As used herein, the term “accuracy,” when referring to a magnetic fieldsensor, is used to refer to a variety of aspects of the magnetic fieldsensor. These aspects include, but are not limited to, an ability of themagnetic field sensor to differentiate: a gear tooth from a gear valley(or, more generally, the presence of a ferromagnetic object from theabsence of a ferromagnetic object) when the gear is not rotating and/orwhen the gear is rotating (or, more generally, when a ferromagneticobject is moving or not moving), an ability to differentiate an edge ofa tooth of the gear from the tooth or the valley of the gear (or, moregenerally, the edge of a ferromagnetic object or a change inmagnetization direction of a hard ferromagnetic object), and arotational accuracy with which the edge of the gear tooth is identified(or, more generally, the positional accuracy with which an edge of aferromagnetic object or hard ferromagnetic object can be identified).Ultimately, accuracy refers to output signal edge placement accuracy andconsistency with respect to gear tooth edges passing by the magneticfield sensor.

The terms “parallel” and “perpendicular” are used in various contextsherein. It should be understood that the terms parallel andperpendicular do not require exact perpendicularity or exactparallelism, but instead it is intended that normal manufacturingtolerances apply, which tolerances depend upon the context in which theterms are used. In some instances, the term “substantially” is used tomodify the terms “parallel” or “perpendicular.” In general, use of theterm “substantially” reflects angles that are beyond manufacturingtolerances, for example, within +/−ten degrees.

It is desirable for magnetic field sensors to achieve a certain level oramount of accuracy even in the presence of variations in an air gapbetween the magnetic field sensor and the gear that may change frominstallation to installation or from time to time. It is also desirablefor magnetic field sensors to achieve accuracy even in the presence ofvariations in relative positions of the magnet and the magnetic fieldsensing element within the magnetic field sensor. It is also desirablefor magnetic field sensors to achieve accuracy even in the presence ofunit-to-unit variations in the magnetic field generated by a magnetwithin the magnetic field sensors. It is also desirable for magneticfield sensors to achieve accuracy even in the presence of variations ofan axial rotation of the magnetic field sensors relative to the gear. Itis also desirable for magnetic field sensors to achieve accuracy even inthe presence of temperature variations of the magnetic field sensors.

As used herein, the term “processor” is used to describe an electroniccircuit that performs a function, an operation, or a sequence ofoperations. The function, operation, or sequence of operations can behard coded into the electronic circuit or soft coded by way ofinstructions held in a memory device. A “processor” can perform thefunction, operation, or sequence of operations using digital values orusing analog signals.

In some embodiments, the “processor” can be embodied in an applicationspecific integrated circuit (ASIC), which can be an analog ASIC or adigital ASIC. In some embodiments, the “processor” can be embodied in amicroprocessor with associated program memory. In some embodiments, the“processor” can be embodied in a discrete electronic circuit, which canbe an analog or digital.

A processor can contain internal processors or internal modules thatperform portions of the function, operation, or sequence of operationsof the processor. Similarly, a module can contain internal processors orinternal modules that perform portions of the function, operation, orsequence of operations of the module.

It should be understood that electronic functions that may be describedbelow to be analog functions can instead be implemented in digitalcircuits, in processors, or in modules. For example, it will berecognized that a comparator can be implemented as an analog comparatorthat compares analog voltages, as a digital comparator that comparesdigital values, or as a processor or module that compares digitalvalues. Examples shown herein to be analog examples do not limit thescope of described embodiments to be analog embodiments only.

As used herein, the term “predetermined,” when referring to a value orsignal, is used to refer to a value or signal that is set, or fixed, inthe factory at the time of manufacture, or by external means, e.g.,programming, thereafter. As used herein, the term “determined,” whenreferring to a value or signal, is used to refer to a value or signalthat is identified by a circuit during operation, after manufacture.

As used herein, the term “active electronic component” is used todescribe and electronic component that has at least one p-n junction. Atransistor, a diode, and a logic gate are examples of active electroniccomponents. In contrast, as used herein, the term “passive electroniccomponent” as used to describe an electronic component that does nothave at least one p-n junction. A capacitor and a resistor are examplesof passive electronic components.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent that other embodimentsincorporating these concepts, structures and techniques may be used.Accordingly, it is submitted that the scope of the patent should not belimited to the described embodiments but rather should be limited onlyby the spirit and scope of the following claims. All references citedherein are hereby incorporated herein by reference in their entirety.

What is claimed is:
 1. A magnetic field sensor for measuring movement ofa target, the magnetic field sensor comprising: a substrate having afirst and second surfaces; a magnet disposed proximate to the firstsurface, wherein the magnet includes at least two poles to generate amagnetic field; and a first bridge structure having a first plurality ofmagnetic field sensing elements configured to generate a first magneticfield signal indicative of a position of the target and a secondplurality of magnetic field sensing elements configured to generate asecond magnetic field signal indicative of the position of the target,wherein a first pair of magnetic field sensing elements of the firstplurality of magnetic field sensing elements are spaced a first distancefrom each other and a second pair of magnetic field sensing elements ofthe second plurality of magnetic field sensing elements are spaced asecond, different distance from each other; wherein an axis ofsensitivity of the first and second pluralities of magnetic fieldsensing elements is rotated at a predetermined angle with respect to anaxis of rotation of the target, and wherein the first bridge structureis configured to generate an output signal based on the first magneticfield signal and the second magnetic field signal, the output signalcorresponding to the position of the target and a change in a propertyof the magnetic field generated by the magnet.
 2. The magnetic fieldsensor of claim 1, wherein first and second magnetic field sensingelements of the first plurality of magnetic field sensing elements arespaced equidistant from a first center axis of the magnet.
 3. Themagnetic field sensor of claim 1, wherein first and second magneticfield sensing elements of the second plurality of magnetic field sensingelements are spaced equidistant from a first center axis of the magnet.4. The magnetic field sensor of claim 1, wherein the first distancebetween first pair of magnetic field sensing elements of the firstplurality of magnetic field sensing elements is less than the seconddistance between second pair of magnetic field sensing elements of thesecond plurality of magnetic field sensing elements.
 5. The magneticfield sensor of claim 1, wherein first and second magnetic field sensingelements of the first plurality of magnetic field sensing elements arespaced equidistant from a first center axis of the magnet and third andfourth magnetic field sensing elements of the first plurality ofmagnetic field sensing elements are spaced equidistant from the firstcenter axis of the magnet, and wherein the first and third magneticfield sensing elements are spaced equidistant from a second center axisof the magnet and the second and fourth magnetic field sensing elementsare spaced equidistant from the second center axis of the magnet.
 6. Themagnetic field sensor of claim 1, wherein first and second magneticfield sensing elements of the second plurality of magnetic field sensingelements are spaced equidistant from a first center axis of the magnetand third and fourth magnetic field sensing elements of the secondplurality of magnetic field sensing elements are spaced equidistant fromthe first center axis of the magnet, and wherein the first and thirdmagnetic field sensing elements are spaced equidistant from a secondcenter axis of the magnet and the second and fourth magnetic fieldsensing elements are spaced equidistant from the second center axis ofthe magnet.
 7. The magnetic field sensor of claim 1, further comprisinga second bridge structure having a third plurality of magnetic fieldsensing elements and a fourth plurality of magnetic field sensingelements, wherein a first pair of magnetic field sensing elements of thethird plurality of magnetic field sensing elements are spaced a firstdistance from each other and a second pair of magnetic field sensingelements of the fourth plurality of magnetic field sensing elements arespaced a second, different distance from each other.
 8. The magneticfield sensor of claim 1, wherein the first magnetic field signalcorresponds to a first degree of contraction of the magnetic fieldgenerated by the magnet in response to the position of the target andthe second magnetic field signal corresponds to a second, differentdegree of contraction of the magnet field generated by the magnet inresponse to the position of the target.
 9. The magnetic field sensor ofclaim 1, further comprising a circuit coupled to the first bridgestructure, wherein the circuit comprises a comparison device having afirst input coupled to a first output of the first bridge structure toreceive the first magnetic field signal and a second input coupled to asecond output of the first bridge structure to receive the secondmagnetic field signal.
 10. The magnetic field sensor of claim 9, whereinthe circuit further comprises an offset module coupled to the first andsecond outputs of the first bridge structure, wherein the offset moduleis configured to provide an offset adjustment to the first and secondmagnetic field signals.
 11. The magnetic field sensor of claim 9,wherein the circuit further comprises a converter module having an inputcoupled to the output of the comparison device.
 12. The magnetic fieldsensor of claim 1, wherein the axis of sensitivity of the first andsecond plurality of magnetic field sensing elements is perpendicular tothe axis of rotation of the target.
 13. The magnetic field sensor ofclaim 1, wherein the predetermined angle ranges from about 0 degreeswith respect to the axis of rotation of the target to about 90 degreeswith respect to the axis of rotation of the target.
 14. The magneticfield sensor of claim 1, wherein the first plurality of magnetic fieldsensing elements comprises a first plurality of magnetoresistanceelements and the second plurality of magnetic field sensing elementscomprises a second plurality of magnetoresistance elements.
 15. Themagnetic field sensor of claim 14, wherein the first and secondpluralities of magnetoresistance elements comprise one or more of giantmagnetoresistance (GMR) elements, anisotropic magnetoresistance (AMR)elements, tunneling magnetoresistance (TMR) elements or magnetic tunneljunction (MTJ) elements.
 16. A method for measuring movement of atarget, the method comprising: positioning a magnetic field sensorrelative to the target, wherein the magnetic field sensor includes: asubstrate having a first and second surfaces; a magnet disposedproximate to the first surface, wherein the magnet includes at least twopoles to generate a magnetic field; and a first bridge structure havingfirst and second pluralities of magnetic field sensing elements, whereina first pair of magnetic field sensing elements of the first pluralityof magnetic field sensing elements are spaced a first distance from eachother and a second pair of magnetic field sensing elements of the secondplurality of magnetic field sensing elements are spaced a second,different distance from each other, and wherein an axis of sensitivityof first and second pluralities of magnetic field sensing elements isrotated at a predetermined angle with respect to an axis of rotation ofthe target; and generating a first magnetic field signal indicative bythe first plurality of magnetic field sensing elements, wherein thefirst magnetic field structure is indicative of a position of thetarget; generating a second magnetic field signal by the secondplurality of magnetic field sensing elements, wherein the secondmagnetic field signal indicative of the position of the target;generating an output signal based on the first magnetic field signal andthe second magnetic field signal, wherein the output signal correspondsto the position of the target and a change in a property of the magneticfield generated by the magnet.
 17. The method of claim 16, furthercomprising spacing first and second magnetic field sensing elements ofthe first plurality of magnetic field sensing elements equidistant froma first center axis of the magnet.
 18. The method of claim 16, furthercomprising spacing first and second magnetic field sensing elements ofthe second plurality of magnetic field sensing elements equidistant froma first center axis of the magnet.
 19. The method of claim 16, whereinthe first distance between the first pair of magnetic field sensingelements of the first plurality of magnetic field sensing elements isless than the second distance between the second pair of magnetic fieldsensing elements of the second plurality of magnetic field sensingelements.
 20. The method of claim 16, magnetic field sensor of claim 1,wherein first and second magnetic field sensing elements of the firstplurality of magnetic field sensing elements are spaced equidistant froma first center axis of the magnet and third and fourth magnetic fieldsensing elements of the first plurality of magnetic field sensingelements are spaced equidistant from the first center axis of themagnet, and wherein the first and third magnetic field sensing elementsare spaced equidistant from a second center axis of the magnet and thesecond and fourth magnetic field sensing elements are spaced equidistantfrom the second center axis of the magnet.
 21. The method of claim 16,wherein first and second magnetic field sensing elements of the secondplurality of magnetic field sensing elements are spaced equidistant froma first center axis of the magnet and third and fourth magnetic fieldsensing elements of the second plurality of magnetic field sensingelements are spaced equidistant from the first center axis of themagnet, and wherein the first and third magnetic field sensing elementsare spaced equidistant from a second center axis of the magnet and thesecond and fourth magnetic field sensing elements are spaced equidistantfrom the second center axis of the magnet.
 22. The method of claim 16,wherein the magnetic field sensor comprises a second bridge structurehaving a third plurality of magnetic field sensing elements and a fourthplurality of magnetic field sensing elements, wherein a first pair ofmagnetic field sensing elements of the third plurality of magnetic fieldsensing elements are spaced a first distance from each other and asecond pair of magnetic field sensing elements of the fourth pluralityof magnetic field sensing elements are spaced a second, differentdistance from each other.
 23. The method of claim 16, wherein the firstmagnetic field signal corresponds to a first degree of contraction ofthe magnetic field generated by the magnet in response to the positionof the target and the second magnetic field signal corresponds to asecond, different degree of contraction of the magnet field generated bythe magnet in response to the position of the target.
 24. The method ofclaim 16, wherein the magnetic field sensor further comprises a circuitcoupled to the first bridge structure, wherein the circuit comprises acomparison device having a first input coupled to a first output of thefirst bridge structure to receive the first magnetic field signal and asecond input coupled to a second output of the first bridge structure toreceive the second magnetic field signal.
 25. The method of claim 24,further comprising providing an offset adjustment, by an offset module,the first and second magnetic field signals.
 26. The method of claim 24,further comprising converting an comparison signal generated by thecomparison device from an analog signal to a digital signal.
 27. Themethod of claim 16, wherein the axis of sensitivity of the first andsecond plurality of magnetic field sensing elements is perpendicular tothe axis of rotation of the target.
 28. The method of claim 16, whereinthe predetermined angle ranges from about 0 degrees with respect to theaxis of rotation of the target to about 90 degrees with respect to theaxis of rotation of the target.
 29. The method of claim 16, wherein thefirst plurality of magnetic field sensing elements comprises a firstplurality of magnetoresistance elements and the second plurality ofmagnetic field sensing elements comprises a second plurality ofmagnetoresistance elements.
 30. The method of claim 29, wherein thefirst and second pluralities of magnetoresistance elements comprise oneor more of giant magnetoresistance (GMR) elements, anisotropicmagnetoresistance (AMR) elements, tunneling magnetoresistance (TMR)elements or magnetic tunnel junction (MTJ) elements.
 31. The methodaccording to claim 16, wherein the target has a sinusoidal profile,wherein sine and cosine signals generated by the target can be combinedto generate an angular position of the target.
 32. The method accordingto claim 31, wherein the sinusoidal profile includes at least oneharmonic to reduce angle error of the angular position of the target.33. A magnetic field sensor for measuring movement of a target, themagnetic field sensor comprising: a substrate having a first and secondsurfaces; a means for generating a magnetic field disposed proximate tothe first surface, wherein the means for generating includes at leasttwo poles; and a first sensing means having a first plurality ofmagnetic field sensing means configured to generate a first magneticfield signal indicative of a position of the target and a secondplurality of magnetic field sensing means configured to generate asecond magnetic field signal indicative of the position of the target,wherein a first pair of magnetic field sensing means of the firstplurality of magnetic field sensing means are spaced a first distancefrom each other and a second pair of magnetic field sensing means of thesecond plurality of magnetic field sensing means are spaced a second,different distance from each other; wherein an axis of sensitivity ofthe first and second pluralities of magnetic field sensing means isrotated at a predetermined angle with respect to an axis of rotation ofthe target, and wherein the first sensing means is configured togenerate an output signal based on the first magnetic field signal andthe second magnetic field signal, the output signal corresponding to theposition of the target and a change in a property of the magnetic fieldgenerated by the means for generating.
 34. The magnetic field sensor ofclaim 33, wherein first and second magnetic field sensing means of thefirst plurality of magnetic field sensing means are spaced equidistantfrom a first center axis of the means for generating.
 35. The magneticfield sensor of claim 33, wherein first and second magnetic fieldsensing means of the second plurality of magnetic field sensing meansare spaced equidistant from a first center axis of the means forgenerating.
 36. The magnetic field sensor of claim 33, wherein the firstdistance between first pair of magnetic field sensing means of the firstplurality of magnetic field sensing means is less than the seconddistance between second pair of magnetic field sensing means of thesecond plurality of magnetic field sensing means.
 37. The magnetic fieldsensor of claim 33, wherein first and second magnetic field sensingmeans of the first plurality of magnetic field sensing means are spacedequidistant from a first center axis of the means for generating andthird and fourth magnetic field sensing means of the first plurality ofmagnetic field sensing means are spaced equidistant from the firstcenter axis of the means for generating, and wherein the first and thirdmagnetic field sensing means are spaced equidistant from a second centeraxis of the means for generating and the second and fourth magneticfield sensing means are spaced equidistant from the second center axisof the means for generating.
 38. The magnetic field sensor of claim 33,wherein first and second magnetic field sensing means of the secondplurality of magnetic field sensing means are spaced equidistant from afirst center axis of the means for generating and third and fourthmagnetic field sensing means of the second plurality of magnetic fieldsensing means are spaced equidistant from the first center axis of themeans for generating, and wherein the first and third magnetic fieldsensing means are spaced equidistant from a second center axis of themeans for generating and the second and fourth magnetic field sensingmeans are spaced equidistant from the second center axis of the meansfor generating.
 39. The magnetic field sensor of claim 33, furthercomprising a second sensing means having a third plurality of magneticfield sensing means and a fourth plurality of magnetic field sensingmeans, wherein a first pair of magnetic field sensing means of the thirdplurality of magnetic field sensing means are spaced a first distancefrom each other and a second pair of magnetic field sensing means of thefourth plurality of magnetic field sensing means are spaced a second,different distance from each other.
 40. The magnetic field sensor ofclaim 33, wherein the first magnetic field signal corresponds to a firstdegree of contraction of the magnetic field generated by the means forgenerating in response to the position of the target and the secondmagnetic field signal corresponds to a second, different degree ofcontraction of the magnet field generated by the means for generating inresponse to the position of the target.
 41. The magnetic field sensor ofclaim 33, further comprising a circuit coupled to the first bridgestructure, wherein the circuit comprises a comparison device having afirst input coupled to a first output of the first sensing means toreceive the first magnetic field signal and a second input coupled to asecond output of the first sensing means to receive the second magneticfield signal.
 42. The magnetic field sensor of claim 41, wherein thecircuit further comprises an offset module coupled to the first andsecond outputs of the first sensing means, wherein the offset module isconfigured to provide an offset adjustment to the first and secondmagnetic field signals.
 43. The magnetic field sensor of claim 41,wherein the circuit further comprises a converter module having an inputcoupled to the output of the comparison device.
 44. The magnetic fieldsensor of claim 33, wherein the axis of sensitivity of the first andsecond plurality of magnetic field sensing means is perpendicular to theaxis of rotation of the target.
 45. The magnetic field sensor of claim33, wherein the predetermined angle ranges from about 0 degrees withrespect to the axis of rotation of the target to about 90 degrees withrespect to the axis of rotation of the target.
 46. The magnetic fieldsensor of claim 33, wherein the first plurality of magnetic fieldsensing means comprises a first plurality of magnetoresistance elementsand the second plurality of magnetic field sensing elements comprises asecond plurality of magnetoresistance elements.
 47. The magnetic fieldsensor of claim 46, wherein the first and second pluralities ofmagnetoresistance elements comprise one or more of giantmagnetoresistance (GMR) elements, anisotropic magnetoresistance (AMR)elements, tunneling magnetoresistance (TMR) elements or magnetic tunneljunction (MTJ) elements.